Claudius Ptolemy is a famous ancient scholar.Ptolemy is famous for his works and specialization in astronomy, geography, cartography, mathematics, and astrology. His works range from the Almagest, a series of thirteen books dedicated to astronomy. The use of mathematics to was used to prove his theories and observations of an Earth-centered universe. His works on astronomy, such as the Geocentric model, are well renowned for their Earth-centered theories. Ptolemy’s theories and works lasted for thousands of years until astronomers such as Galileo, Copernicus, and Kepler came into the picture to test their theories against the longstanding theory of Ptolemy’s geocentric model. Not only was Ptolemy famous for his works on astronomy and the Almagest but the famous Greek was also fond of astrology from a scientific view point. Astrology was an important study back in ancient Greece and Ptolemy’s skills did not leave that off of his knowledge. He published one of the most famous books in astrology named the Tetrabiblos. The addition of the Geographia by Ptolemy himself allowed the Greeks to excel their understanding of their environments geography.
Claudius Ptolemy was born in Alexandria, Egypt around 90 AD. Some information differs on the originality of the name Ptolemy. For example, the name Ptolemy was a common name in ancient Greece. “Claudius” came from the first Roman rule of Egypt as a common name. Following the lost of Roman rule, Ptolemy I Soter, a Macedonian general of Alexander the Great became Egypt’s ruler.
The general idea of planets and their motion in Ptolemy’s era was that the planets and heavens are all perfect. Although the Greeks knew that the Earth was round from observing lunar eclipses, their accepted theory was that the Earth was at the center of the universe with all of the planets moving around it in a perfect orbit; in addition, Greeks assumed that since they could not feel the Earth moving then it is a stationary planet compared to the other planets and stars that revolved around them. The Greeks were obsessed with the perfection of nature and believed their Earth belonged in the center of the universe; however, this theory had questions on why planets would have a backwards or retrograde motion. Questions such as why some planets and the Sun are brighter or dimmer during parts of the day had left people like Ptolemy performing in depth observations.
The geocentric model is a model of the universe with the Earth in the middle. Ptolemy's epicycle showed that the celestial bodies orbiting around Earth also exhibited their own circular orbit. The Earth did not move while all of the other planets orbited around Earth in a uniform circular motion. Ptolemy’s use of epicycles explains the retrograde motion of why planets seemed to orbit backwards to the Greeks. This claim by Ptolemy allowed the Greeks to continue on their Geocentric theory using Ptolemy’s observations as a basis for answering previous questions.
Over time Ptolemy began to answer some questions that were associated with the Greeks view of their universe by incorporating epicycles into his work within a revelation of books and reports. Epicycles are defined as a combination of circular movements in which a planet or object use as a pathway. Imagine Earth being the center of the universe like the Greeks assumed. Mars orbits Earth and exhibits a retrograde motion in which Greek astronomers could not explain. Ptolemy comes into the picture and explains that Mars goes retrograde because it runs on an epicycle, a small circle while orbiting Earth; in addition, the small epicycle that Mars runs on is orbiting a deferent or larger circle.
Ptolemy combined his astronomy, mathematical calculations, and theories into The Almagest. His thirteen book series was compiled at about 150 AD. The Almagest consisted of previous and older studies of the Babylonians and Greek works that Ptolemy used. The early works of Greek astronomer Hipparchus are included as well. Ptolemy modified Hipparchus’ explanation of planetary motions by inventing the equant and the eccentric to provide a more accurate explanation. Ptolemy simplified those works of the two cultures by including mathematics such as trigonometry. He also reached further into their studies by applying his principles and theories.
Ptolemy divided the Almagest into thirteen volumes. He explains the Geocentric model as a basis for continuing the other books but Ptolemy also introduces the readers to trigonometry and the trigonometry tables associated with his observations of planetary movements. The Almagest covers what people see above the skies such as the rise and setting of moon and sun. Ptolemy explains the Sun and the Moons movements with the addition of defining precession of equinoxes and epicycles to readers. The observation of the distances of our Sun and moon from the Earth are also covered in Volumes IV and V.
The Almagest's dominance and popularity overshadowed that of Ptolemy's Tetrabiblos. Ptolemy's Tetrabiblos was not widely acclaimed like that of the Almagest but the influence and popularity of the Tetrabiblos amongst astrologers equals to that of the Bible amongst religious scholars. The Tetrabiblos is a four volume book based on astrology. Ptolemy was strictly a scientist but he saw astrology not as superstition but as a way of how humans operated due to the planetary motions and the pressure of the atmosphere affecting their lives. “Ptolemy explains how the constant movement of the planets creates an ever-changing atmosphere to which all the Earth's creatures are sensitive. Just as two similar seeds grow differently as a result of their environment, so is each soul affected by the celestial atmosphere at the time of its birth.” (Houlding)
Houlding claims that the relationship between the Earths creatures and the atmosphere relates to the science of nature. The Tetrabiblos consists of astronomical data gathered from past observations as well as an interpretation of astrology from a philosophical view.
"the Tetrabiblos shows a noticeable lack of interest in the houses, whilst other elements of astrology were considered to be completely unworthy of mention, either because they were too unscientific, too reminiscent of fortune telling..."
Ptolemy left out the mythical aspects of astrology because they were too fictitious to explain in a scientific manner. Ptolemy’s interest in astrology focuses on the scientific explanations to make Astrology more as a credible source of science rather than being a source of lore and fortunes.
Geography and mapping were difficult missions to accomplish back in Ptolemys era of limited technology. The Greek geographers used math and manual labor to create a map of their lands. Ptolemy is known for using a variety of past scholars works to boost his theories as more credible and geography is no different. Ptolemy mapped out the known world at his time with the help of past geographers of the Roman and Persian empire of the time. Coordinates and Latitude lines were one of the most popular methods that Ptolemy uses in his Geographia.
Ptolemy’s legacy continues on in the form of his famous books The Almagest and The Tetrabiblos. His works of the Almagest provided the ancient world a greater understanding of how the planets, stars, and moons operated in the universe. Ptolemy’s astronomy based book would continue to dominate astronomical debates for centuries. Ptolemy’s skill into geography helped establish a basis for future geographers to excel their mapping abilities with accurate detail. The Tetrabiblos, the astrological counter-part of The Almagest, is still a popular book amongst astrologists seeking to understand astrology in a scientific manner. His Geocentric model of an Earth-centered universe survived for centuries before the arrival of Copernicus and the Heliocentric model.
Future astronomers such as Galileo and Copernicus’ studies have proven that the Earth is not the center of the universe; however, Ptolemy’s centuries of popularity before Galileo and Copernicus survived in the form of thousands of reprints such as ancient scriptures from Roman, Greek, and Arab empires. Ptolemy’s work within the Almagest and the Geocentric model has long been used for centuries before those two men’s era Arab and Western nations would continue on Ptolemy’s work until they would be disproven in the 1600’s.

Reference Page
The Ptolemaic Model. (n.d.). Polaris Project. Retrieved October 18, 2012, from http://www.polaris.iastate.edu/EveningStar
Greek Astronomy. (n.d.). ibiblio - The Public's Library and Digital Archive. Retrieved October 21, 2012, from http://www.ibiblio.org/expo/vatican.exhibit/exhibit/d-mathematics/Greek_astro.html